Circulation control airfoil system

ABSTRACT

A lifting airfoil has the capability of exhibiting a coanda profile, or blunt trailing edge for low speed landings capability, and a blown flap or jet flap for high speed transonic operation. The airfoil may be a supercritical type employing a flap which can be rotated to combine with the airfoil to produce a coanda profile or which can be used as a blown flap at transonic speeds when combined with a high velocity blowing jet over the flap. In addition, the supercritical airfoil can include a slot in the underside of the foil for blowing a jet flap in lieu of the blown flap.

United States Patent [191 Williams et a].

[4 1 Oct. 9, 1973 CIRCULATION CONTROL AIRFOIL SYSTEM represented by theSecretary of the Navy 221 Filed: Dec. 7, 1970 21 Appl. No.: 95,648

[56] References Cited UNITED STATES PATENTS 3/1964 Alvarez-Calderon...l244/42 DB 3/1968 Alvarez-Calderon 244/42 DB 3,447,763 6/1969 Allcock244/42 DA Primary Examiner-Milton Buchler Assistant Examiner-Carl A.Rutledge Attorney-R. S. Sciascia and Q. E. Hodges [57] ABSTRACT Alifting airfoil has the capability of exhibiting a coanda profile, orblunt trailing edge for low speed landings capability, and a blown flapor jet flap for high speed transonic operation. The airfoil may be asupercritical type employing a flap which can be rotated to combine withthe airfoil to produce a coanda profile or which can be used as a blownflap at transonic speeds when combined with a high velocity blowing jetover the flap. In addition, the supercritical airfoil can include a slotin the underside of the foil for blowing a jet flap in lieu of the blownflap.

12 Claims, 5 Drawing Figures Patented Oct. 9, 1-973 3,764,092

INVENTORS ROBERT M. WILLIAMS BY RICHARD D. MURPHY AT ORNEY CIRCULATIONCONTROL AIRFOIL SYSTEM The invention described herein may bemanufactured and used by or for the Government of the United States ofAmerica for Governmental purposes without the payment of any royaltiesthereon or therefor.

DESCRIPTION OF THE PRIOR ART The prior art shows the blunt tail orcirculation control airfoil utilizes tangential blowing. The prior artadditionally shows the use of a blown flap where circulation control ismaintained over the surface of a flap by blowing ajet of air across it.However, each of these devices have been used in a separate airfoil,each airfoil lacking the capability of changing its shape and adaptingto both low speed and high speed operation.

SUMMARY This invention pertains to an airfoil which is adaptable forhigh speed, transonic operation which is additionally adaptable for lowspeed landing applications. A supercritical airfoil utilizing reversecamber near its trailing edge and designed for high speed, high machnumber operation, comprises a flap at its trailing edge. For high speedoperation, the flap aligns itself with the airfoil, becoming a part ofthe airfoil. At cruising speed the supercritical airfoil shape ismaintained, retaining its efficiency. At high mach or transonic speedand where a combat situation is encountered, requiring increased lift,blowing can be initiated over the flap, altering the pressuredistribution and developing increased lift. For a low speed operation,the supercritical shape of the airfoil can be altered specifically tomeet low speed requirements. The flap can be rotated forming a blunttrailing surface or coanda profile with the airfoil. A thin sheet of airis blown out over the length of the blunt edge through a series ofnozzles arranged in a tangential slot, coextensive with the blunt edgeand adjacent to it. The thin slieet of air is blown tangentially outover the trailing edge and adheres to the trailing edge, detaching fromthe airfoil at a point on the foil underside, below the trailing edgeand determined by the intensity of the blowing. The circulation controlover the blunt edge through tangential blowing, increases the lift by asignificant amount over a conventional airfoil, employing such devicesas leading edge slots, trailing edge flap and boundary layer control inthe leading and trailing edges.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. la, lb, and 1c, shows incross-section, the preferred embodiment airfoil with thei flap arrangedfor three modes of operation; FIG. Ia for high speed, FIG. lb for speedsapproaching landing speeds, and FIG. lc for landing speed.

FIG. 2 shows an alternative embodiment, in crosssection, where for lowspeed operation the flap is arranged in a non-loaded floating positionand exposing the airfoil blunt edge for circulation control tangentialblowing.

FIG. 3 shows an alternative embodiment in crosssection, for high speedoperation, utilizing the jet flap instead of the blown flap shown inFIG. Ia.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. la,wherein is shown the main wing or main airfoil 10 having the leadingedge 11, a second edge 13, adjacent to flap l5, and a tangential slots21 and 22, adjacent the flap. Flap 15 is hinged to airfoil 10, by hingepin 17. The airfoil is shown in crosssection and slots 21 and 22 extendthe length of the span. As shown in FIG. la, the airfoil and the flapare arranged for high speed operation. In the high speed range, the foiland the flap form one continuous airfoil upper surface, except for thediscontinuity introduced by slots 21 and 22. Flap 15 is shaped tointroduce a negative camber at area 19. For a transonic operation wherehigh lift is required air, shown by arrow 23, is blown from slot 21,across the flap upper surface. The blown flap changes the pressuredistribution across the foil upper surface, dislacing the shock furtheraft on the airfoil, thus maintaining a larger working portion on theairfoil and developing increased lift.

FIG. lb, shows the airfoil of FIG. 1a, in a low speed situation as whenthe aircraft is approaching a landing and requires increased flap angle.The flap is rotated downward from the position assumed in FIG. 1a, toprovide the increased flap angle. In addition, a thin sheet of air,shown by arrow 25, is blown out of slot 21 and across the upper surfaceof flap 15 to provide increased blown flap lift as in the case of FIG.1a.

FIG. 10, the flap 15 is rotated so that its under surface 18, is incontact with its mating surface 16, on the lower side of foil 10. Inthis position, the flap in conjunction with the foil, forms a blunttrailing surface denoted by bracket 29, over which a thin sheet of airflows as shown by arrow 27, and which is produced by tangential blowingout of slot 21.

Referring now to FIG. 2, is shown an alternate embodiment, wherein flap15 is moved aft of foil 10, in a free floating position, within the flowstream as shown by arrows 28 and 31, wherein no load on flap 15 isproduced. The flap 15 is displaced sufficiently aft of the foil 10, sothat the coanda profile at blunt trailing edge 14, and the circulationof air blown from tangential slot 21, around the blunt trailing edge isuneffected by the presence of flap 15. This embodiment would be used insubstitution of the embodiment shown in FIG. 10, where the flap isrotated against the foil 10.

In FIG. 3, is shown an alternative embodiment to that shown in FIG. 1a,for high speed or transonic operation wherein a jet flap is produced byblowing ajet of air 33 out of slot 32. This arrangement would be insubstitution of blowing air across the upper surface of flap 15, asshown in FIG. 1a. The flap alters the pressure distribution as does theblown flap, to move shock on the upper surface aft, thereby developing alarger working portion of the airfoil for developing lift with theconsequent result of higher lift. The arrangement of FIG. 2, for movingthe flap aft can be used with the arrangement in FIG. la, wherein air isblown from the tangential slot out across the upper surface of theairfoil or FIG. 3, where the stream of air is blown out of slot 32,producing a jet flap. Similarly, in the arrangement of FIG. 3, whereinthe jet flap is produced by blowing out of slot within the flap can beused in low speed application by stopping the flow of air from slot 32and rotating flap 15 to the position shown in FIG. 10, and blowing airtangentially out over the blunt surface 29, as shown in FIG. 1c, fromthe slot 21.

An additional slot 22 is shown on foil 10, forward of slot 21, is shown.This slot 22 is used to increase lift where the foil 10 is in a highangle of attack.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is: 1

1. An airfoil producing high lift at low landing speeds and at transonicspeeds, comprising:

a main wing;

a flap having a sharp trailing edge, mounted for pivoting movement alongthe rearward edge of the main wing; and

said flap being rotatable against the underside of said main wing toform a blunt trailing edge for circulation control blowing.

2. The airfoil of claim 1, wherein:

said main wing has a first slot disposed along its rearward edgeadjacent said flap for tangentially blowing air over said blunt edge atlow speeds and over said sharp edge at transonic speeds.

3. The airfoil of claim 2 wherein said flap is rotatable to form asupercritical airfoil with said main wing; and said supercritical mainwing having negative camber over the upper surface of said airfoil.

4. The lifting foil of claim 3 wherein said flap can be rotated betweensaid blunt edge position and said supercritical airfoil position to forma continuous surface with the underside of said main wing for providingadditional lifting surface.

5. The lifting foil of claim 3 wherein air is blown out said slot acrossthe upper surface of said flap to form a blown flap.

6. A lifting foil for producing high lift at low landing speeds and attransonic speeds, comprising:

a main wing;

a blunt trailing edge on said main wing;

a flap disposed along said blunt trailing edge;

said flap having a sharp trailing edge;

said flap being movable rearward of the main wing to a free streamposition, exposing the blunt trailing edge for circulation control bytangential blowing.

7. The airfoil of claim 6, wherein:

said main wing has a first slot disposed along the trailing edgeadjacent to said blunt edge for tangentially blowing air over said flapedge at transonic speeds and over said blunt edge at low speeds.

8. The lifting foil of claim 7 wherein said flap is moveable againstsaid blunt trailing edge to form a substantially continuous liftingsurface.

9. The lifting foil of claim 8, wherein:

said airfoil has a negative camber portion on its upper surface forforming a supercritical airfoil.

10. An airfoil producing high lift at low landing speeds and attransonic speeds, comprising:

a flap having a sharp trailing edge, mounted for pivoting movement alongthe rearward edge of the airfoil, said flap being rotatable against theunderside of said airfoil to form a blunt trailing edge for circulationcontrol blowing, wherein said flap is rotatable to form a supercriticalairfoil with said lifting airfoil said airfoil having a first slotdisposed along its rearward edge adjacent to said flap for tangentiallyblowing air over said blunt edge at low speed and over said sharp edgeat transonic speeds;

said supercritical airfoil having negative camber over the surface ofsaid airfoil, wherein air is blown out of said slot across the uppersurface of said flap to form a blown flap; and

a second slot in said airfoil parallel to said first slot and forward ofsaid first slot.

11. An airfoil producing high lift at low landing speeds and attransonic speeds, comprising:

a flap having a sharp trailing edge, mounted for pivoting movement alongthe rearward edge of the airfoil, said flap being rotatable against theunderside of said airfoil to form a blunt trailing edge for circulationcontrol blowing, wherein said flap is rotatable to form a supercriticalairfoil with said lifting airfoil;

said airfoil having a first slot disposed along its rearward edgeadjacent to said flap for tangentially blowing air over said blunt edgeat low speed and over said sharp edge at transonic speeds;

said supercritical airfoil having negative camber over the surface ofsaid airfoil, wherein air is blown out of said slot across the uppersurface of said flap to form a blown flap; and

said flap has a slot in its bottom surface for blowing a jet of airthrough said slot to produce a jet flap where said flap is rotated toform a supercritical lifting foil with said airfoil.

12. A lifting airfoil for producing high lift at low landing speeds andat transonic speeds comprising:

a blunt trailing edge;

a flap disposed along said blunt trailing edge;

said flap having a sharp trailing edge;

said flap being movable rearward of the airfoil to a free streamposition, exposing the blunt trailing edge for circulation control bytangential blowing;

said airfoil having a first slot disposed along the trailing edgeadjacent said blunt edge for tangentially blowing air over said flapedge at transonic speeds and over said blunt edge at low speeds;

said flap being movable against said blunt trailing edge to form asubstantially continuous lifting surface and said flap causing anegative camber portion on the upper surface of the entire airfoil forforming a supercritical airfoil with said lifting foil; and

said flap having a slot in its underside for blowing a jet of air toproduce a jet flap.

1. An airfoil producing high lift at low landing speeds and at transonic speeds, comprising: a main wing; a flap having a sharp trailing edge, mounted for pivoting movement along the rearward edge of the main wing; and said flap being rotatable against the underside of said main wing to form a blunt trailing edge for circulation control blowing.
 2. The airfoil of claim 1, wherein: said main wing has a first slot disposed along its rearward edge adjacent said flap for tangentially blowing air over said blunt edge at low speeds and over said sharp edge at transonic speeds.
 3. The airfoil of claim 2 wherein said flap is rotatable to form a supercritical airfoil with said main wing; and said supercritical main wing having negative camber over the upper surface of said airfoil.
 4. The lifting foil of claim 3 wherein said flap can be rotated between said blunt edge position and said supercritical airfoil position to form a continuous surface with the underside of said main wing for providing additional lifting surface.
 5. The lifting foil of claim 3 wherein air is blown out said slot across the upper surface of said flap to form a blown flap.
 6. A lifting foil for producing high lift at low landing speeds and at transonic speeds, comprising: a main wing; a blunt trailing edge on said main wing; a flap disposed along said blunt trailing edge; said flap having a sharp trailing edge; said flap being movable rearward of the main wing to a free stream position, exposing the blunt trailing edge for circulation control by tangential blowing.
 7. The airfoil of claim 6, wherein: said main wing has a first slot disposed along the trailing edge adjacent to said blunt edge for tangentially blowing air over said flap edge at transonic speeds and over said blunt edge at low speeds.
 8. The lifting foil of claim 7 wherein said flap is moveable against said blunt trailing edge to form a substantially continuous lifting surface.
 9. The lifting foil of claim 8, wherein: said airfoil has a negative camber portion on its upper surface for forming a supercritical airfoil.
 10. An airfoil producing high lift at low landing speeds and at transonic speeds, comprising: a flap having a sharp trailing edge, mounted for pivoting movement along the rearward edge of the airfoil, said flap being rotatable against the underside of said airfoil to form a blunt trailing edge for circulation control blowing, wherein said flap is rotatable to form a supercritical airfoil with said lifting airfoil said airfoil having a first slot disposed along its rearward edge adjacent to said flap for tangentially blowing air over said blunt edge at low speed and over said sharp edge at transonic speeds; said supercritical airfoil having negative camber over the surface of said airfoil, wherein air is blown out of said slot across the upper surface of said flap to form a blown flap; and a second slot in said airfoil parallel to said first slot and forward of said first slot.
 11. An airfoil producing high lift at low landing speeds and at transonic speeds, comprising: a flap having a sharp trailing edge, mounted for pivoting movement along the rearward edge of the airfoil, said flap being rotatable against the underside of said airfoil to form a blunt trailing edge for circulation control blowing, wherein said flap is rotatable to form a supercritical airfoil with said lifting airfoil; said airfoil having a first slot disposed along its rearward edge adjacent to said flap for tangentially blowing air over said blunt edge at low speed and over said sharp edge at transonic speeds; said supercriticaL airfoil having negative camber over the surface of said airfoil, wherein air is blown out of said slot across the upper surface of said flap to form a blown flap; and said flap has a slot in its bottom surface for blowing a jet of air through said slot to produce a jet flap where said flap is rotated to form a supercritical lifting foil with said airfoil.
 12. A lifting airfoil for producing high lift at low landing speeds and at transonic speeds comprising: a blunt trailing edge; a flap disposed along said blunt trailing edge; said flap having a sharp trailing edge; said flap being movable rearward of the airfoil to a free stream position, exposing the blunt trailing edge for circulation control by tangential blowing; said airfoil having a first slot disposed along the trailing edge adjacent said blunt edge for tangentially blowing air over said flap edge at transonic speeds and over said blunt edge at low speeds; said flap being movable against said blunt trailing edge to form a substantially continuous lifting surface and said flap causing a negative camber portion on the upper surface of the entire airfoil for forming a supercritical airfoil with said lifting foil; and said flap having a slot in its underside for blowing a jet of air to produce a jet flap. 